NMR-based lipidomics of fish from a metal(loid) contaminated wetland show differences consistent with effects on cellular membranes and energy storage

Abstract

Metals and metalloids are priority contaminants due to their non-degradable and bioaccumulative nature, and their ability to regulate and perturb diverse physiological processes in various species. Metal(loid)s are known to cause oxidative stress through production of reactive oxygen species (ROS), thus related endpoints like lipid peroxidation (LPO) have received considerable attention as biomarkers of exposure. However, the implications of metal(loid) toxicity including LPO on actual lipid profiles of species inhabiting contaminated systems are poorly understood. Here we applied Nuclear Magnetic Resonance (NMR) spectroscopy for untargeted lipidomics of mosquitofish (Gambusia holbrooki) collected from reference and metal(loid)-contaminated wetlands. We measured a range of trace elements in water and fish using inductively coupled plasma - mass spectrometry (ICP-MS), and interpreted site differences in the lipid profiles of mosquitofish in the context of known physiological responses to sub-lethal metal(loid) exposure. Results indicate deregulation of cellular membrane lipids (i.e., glycerophospholipids, cholesterol and sphingolipids) and increased energy storage molecules (i.e., triacylglycerols and fatty acids) in fish from the contaminated wetland. These responses are consistent with the recognised induction of oxidative stress pathways in organisms exposed to metal(loid)s and could also be symptomatic of mitochondrial dysfunction and endocrine disruption. It is difficult to attribute metal(loid)s as the sole factor causing differences between wetlands, and a more controlled experimental approach is therefore warranted to further explore mechanistic pathways. Nevertheless, our study highlights the benefits of untargeted ¹H NMR-based lipidomics as a relatively fast and simple approach for field-scale assessment and monitoring of organisms inhabiting metal(loid) contaminated environments.

Keywords: Ecotoxicology; Energy storage; Environmental monitoring; Lipidomics; Nuclear Magnetic Resonance; Oxidative stress.